Along with the recent high integration of semiconductor elements, there is a growing tendency to produce ultra-large scale integrations, and there is a demand for the development of a technology for forming ultrafine patterns having a line width of 0.10 micrometers or less in lithographic processes.
Accordingly, the wavelength of the light used in exposure processes is even shortened from the region of conventionally used g-line and i-line, and therefore, attention is being paid to studies on lithography using far-ultraviolet radiation, KrF excimer laser light, ArF excimer laser light, EUV, X-radiation, electron beam and the like.
Particularly, in connection with the light source, electron beam lithography has been valued as a next-generation or next next-generation pattern formation technology, and in this regard, development of a high sensitivity and high resolution positive type resist is desired.
On the other hand, high sensitivity is in direction relationship with the processing speed of the lithographic process. This is because high sensitivity is related to the power source of an electron beam, and as the sensitivity of a resist is higher, pattern formation is enabled even by a power source with a smaller amount of energy; however, sensitivity is poor, and a power source with a higher amount of energy is required.
However, in the case of an electron beam, the light of the electron beam tends to be absorbed by matter, and therefore, with regard to EUV lithography, there has been an attempt to supplement such a characteristic by using a reflector. However, the reflectors used for EUV lithography do not have a reflection efficiency of 100% so that there are difficulties in enhancing the performance of power sources.
In regard to positive resists for electron beam, since sensitivity, resolution and line edge roughness are in a complementary relationship of trading off each other, when an increase in the sensitivity is promoted, the resolution is decreased, and line edge roughness is deteriorated. Therefore, there is a strong demand for the development of a resist which can satisfy the characteristics of sensitivity, resolution and line edge roughness all at the same time.
Conventional resist materials that have been generally used for g-line, i-line, KrF and ArF are chemically amplified resists (CAR), and copolymers produced by radical polymerization have been mainly used.
Specifically, when a solution of a polymer resist material such as polymethyl methacrylate, polyhydroxystyrene having an acid-dissociating reactive group, or polyalkyl methacrylate is applied on a substrate to produce a resist thin film, and the resist thin film is irradiated with ultraviolet radiation, far-ultraviolet radiation, electron beam, extreme ultraviolet radiation, or X-radiation, a line pattern having a line width of about 45 to 100 nm can be formed.
However, such a polymeric resist based on a copolymer generally has a molecular weight as large as about 20,000 to 100,000, and the molecular weight distribution is also relatively broad. Therefore, during the process of forming a fine pattern, roughness is likely to occur, and it is difficult to control the dimension of the pattern, so that the product yield may be lowered. Therefore, there are limitations in pattern miniaturization in the conventional lithographic technology of using polymeric resist materials.
In order to produce finer lithographic patterns, studies have been conducted on various resist materials. But, those single molecule type resist compounds that are currently known have problems such as low etching resistance, a large amount of outgas, low solubility in the safety solvents used in semiconductor production processes, and poor resist pattern shapes. Thus, there is a demand for a novel resist material which can simultaneously satisfy complementary characteristics such as a satisfactory pattern shape with high sensitivity and high resolution, and satisfactory line edge roughness.